Presently Indian Mercs.&: latest E class have Rim size 16.The Rim size 15 keeps my car too low for Indian Roads.Shall the change if possible adding broader tyres effect the efficiency of the engine?
Yes you can fit a 16": rim, but keep in mind that you will want to keep the overall tire diameter the same, so going to a 16": wheel will not raise your car. Based on the tire size you provided, your tire diameter is roughly 25.5":. Your closest sizes for the 16": wheel are 205/60-16, which is slightly bigger at 25.7":, and 215/55-16, which is slightly smaller at 25.3":. You need to stay as close as possible to the original diameter because you will throw off your speedometer, and you may have clearance issues as well.
If you need to gain additional ground clearance, your best bet is to look into replacing your springs for ones made for that purpose.
If you increase the rim size, you should lower the aspect ratio of the tire. So you would be using something like a 205/60/16. These tires would not be broader. If you wanted a broader tire, you could go to a 215/55/16. In neither case would you gain any ride height. The difference in performance and road holding would be negligible.
You should be careful that larger tires don’t cause interference with the body work.
If you want to be higher off of the ground, then get some different springs that would raise your car a couple of inches… You can also go with a bigger rim and then also with a bigger tire (for example 205/65/16, that would also raise your ride), but you should check with your dealer to see what the biggest rim you can put on your car with tires, to safely raise your car…
replace tires with 225 70 r15 .That will give you greater wall height.